Liquid and vapor separating pump



March 1958 LE ROY H. BARR EIAL. 2,826,150

LIQU ID AND VAPOR SEPARATING PUMP 2 Sheets-Sheet 1 Filed Dec. 21. 1954l6 1- a v INVENTORS LeELfi Barn i 5%lrjlgmfyr 2 may March 11, 1958' l4:ROY H. BARR ETAL 5,

uqum AND VAPOR SEPARATING'PUMP -2 Sheets-Sheet 2 Filed Dec. 21, 1954,INVENTORS lie/( 0y ii Barr William fqberm r Y W 2: orney United StatesPatent 1 2,826,150 LIQUID AND VAPOR SEPARATING PUMP Le Roy H. Barr,Elyria, and William F. Stoermer, Grafton, Ohio, assignors to Lear,Incorporated, Grand Rapids, Mich., a corporation of Illinois ApplicationDecember 21, 1954, Serial No. 476,690 Claims. (Cl. 103-113) Thisinvention relates to a pump for liquid fuel. More particularly, it hasreference to a booster pump as frequently employed aboard aircraftadjacent the fuel tank for pressuring gasoline therefrom to anotherpoint in the fuel-feeding system. Customarily, the entire pump,including its driving motor, is submerged in the fuel, for example, asdisclosed in U. S. Letters Patent No. 2,418,221, granted to Russell R.Curtis.

At higher altitudes vaporization of the fuel presents a serious problemas the vapor bubbles rising in the body of fuel are pumped along withfuel and cause interference with operation of the engines, sometimesreferred to as vapor lock. Expressed otherwise, the moment the boilingpoint of the fuel is reached, the same is devoid of sufficient energy tomove into the pump, and such condition is also described as vapor lock.The problem of separating the vapor bubbles occluded in the fuel is byno means new, and has presented a constant challenge to workers in thisart, as exemplified by a large body of patented art which includes theCurtis patent above noted. Accordingly, any elaboration of the problemand its causes is deemed superfluous.

The present invention relates to a fuel booster pump having an improvedarrangement for effecting efficient separation of the occluded vaporfrom the fuel prior to the discharge of the same from the pump outletand the return of the vapor to the fuel supply wherein it rises to thesurface, and the accomplishment of such object by extremely simplemeans.

The invention arrangement performs a dual function, since it not onlyseparates the vapor bubbles from the fuel during periods when violentboiling is not prevalent, but performs a continuous priming actionduring such time as boiling is at a peak rate.

Other objects will become apparent from the ensuing description takentogether with the accompanying drawings, in which latter:

Fig. l is a combined side elevational view and cross section showing theimprovement of the invention;

Fig. 2 is a cross section taken on the line 2-2 of Fig. 1;

Fig. 3 is a cross section taken on the line 3--3 of Fig. 1 and Fig. 4 isa cross section taken on the line 4-4 of Fig. 1.

While the invention will be described in connection with a hydroturbinetype of centrifugal impeller, it will become apparent that the same willfind adaptation to impellers having a configuration differing from theexample.

Turning now to the drawings, there is shown one design of booster pumpincorporating the invention and wherein the numeral designates the bodyor casing of the pump, including means defining a discharge port 12, aninlet port 13 and a volute discharge chamber 14. The body 10 and itstherewith-assembled parts to be described is secured to a wall 15 of thefuel tank through a suitable opening 16. Parenthetically, it will benoted that the port 12 is of the known dual type whereby the associatedoutlet conduit may be connected at either end, whereupon the unusedopening will be suitably closed off. Inlet 13 includes a cylindricalchamber 17 occupied by the customary strainer 18.

A shroud 31 is fitted within a cylindrical opening 32 of the body 10 andis secured thereto by means of screws 33, although the same may, ifdesired, be integral, in whole or part, with the casing 10. A ringgasket 34 serves as a seal. Shroud 31 is provided with a peripheralchannel 35 defining with the wall of the opening 32 an annular passage37, the purpose of which will be detailed hereinafter.

An electric motor 41 is secured, by means of a flange 42 and screws 43to a suitable pad 44 of the body 10 and carries on its shaft 46 acentrifugal or primary impeller 49 and a secondary impeller 51 formingpart of a suitable source of suction, for example, a water-ring pump.

The impeller 49 comprises a hub 52 hearing a plurality of helical vanes53 (Figs. 2 and 4) supported thereon at their upper end and terminatinginwardly on a frustoconical surface 54 or eye of the impeller, althoughnot to be regarded as so limited. At their outer periphery the vanes 53terminate in part on a cylindrical surface 55 and a frusto-conicalsurface 56 likewise not to be regarded as limitative. The surface of theshroud 31 is conformed over part of its extent, namely 58, to theadjacent periphery 56 of the vanes 53 except for the customary runningclearance, as shown.

The configuration of the lower ends of the several vanes 53 is such asto cause them to fall within an annular area A. In the present examplesuch area A has an inner diameter of 1% inches and an outer diameter of1 /2 inches. The angle of the surfaces 56 and 58 to the vertical is 13%and the vertically measured height of the impeller vanes 53 is /8 inch.At their junction with the hub 52 the ends of the vanes fall within anannular area of /1 inch interior diameter and 2 inches exterior diameterand the four vanes shown commence inwardly tangentially to the circleand are provided with an exit angle of 10. Otherwise the same are asfound generally in centrifugal pumps.

The shroud 31 is provided with a shoulder having an annular groove 61preferably of rectangular transverse cross section but which latter maytake other forms as long as an area is defined sufiicient to pass themaximum volume of vapor and/or liquid by-passed thereto by the action ofthe impellers 49 and 51 and as will be elaborated upon hereinafter. Inthe present example the groove 61 has an internal diameter of 1.156inches and an external diameter of 1.389 inches, making an effectivewidth of 0.117 inch approximately, and a depth of 0.097 inch. Thearrangement of the impeller 49 relative to the groove 61 is such thatthe zone A defined by the former is at least equal to the width of thegroove and coextensive therewith. The gap 65 need be only sulficient toafford running clearance.

Groove 61 is in fluid communication, via a passage 66 (Fig. 2) with thepassage 37, and such latter passage is, in turn, in fluid communicationwith a chamber 67 via.

a passage 69. Chamber 67 constitutes the inlet of a second pump, forexample, a water-ring pump which includes the secondary impeller 51 andof which chamber 71 is the outlet. Such outlet communicates, by means ofa conduit, not shown, with the interior of the tank 15 for delivery ofthe recovered vapor and some quantity of fuel thereto.

Operation is as follows: Assuming the pressure in the tank 15 is suchthat fuel vapor is being generated the input to the main pump 23 at 13comprises liquid and occluded vapor which pass upwardly through thethroat 22 to the eye 54 of the impeller 49 and thence into the intervanespaces. Vapor bubbles appearing within the zone of influence of theimpeller vanes are forced, by the separative effect of centrifugal forceto flow to the area of smallest diameter within the rotative effect ofthe vanes,

i. e., to within the inner ends of the passages between the:

Patented Mar. 11, 1958 impeller vanes. If, now, an axial force isapplied at the zone of accumulation of the bubbles the same will bewithdrawn. Thus we provide the groove 61 toward which the bubbles areconstrained to move under the influence of the suction of the secondarypump 20. Concurrently the liquid, being of higher density, is traversedradially and upwardly in the space confined by the wall 58 and outwardlyinto the volute 14 to the pump outlet 12 (Fig. 2). The vapor passes fromthe groove 61 into the passage 37, through the passage 69 and into andthrough the secondary pump 20 for return to the mass of fuel in thetank.

Essentially the improved separation resulting from the inventionstructure is the removal of the vapor as close as may be permitted tothe eye of the impeller without restricting the size of the inlet, andby application of axially applied suction sweeping the bubbles from thefree lower end of the vanes.

It has been recognized that vapor bubbles may be separated from theliquid in a zone near the eye of the impeller. However, prior provisionsfor effecting this end have assumed that the bubbles accumulate at theextreme inner edge of the vanes, whereas we have found that the bubblesare substantially separated from the liquid over a zone extendingoutwardly from the inner edge of the vanes. Accordingly, sweeping of thebubbles from the zone of accumulation. has been found to be accomplishedbest by applying the axial suction over an annular area corresponding tothat portion of the impeller whereat the bubbles have their maximumconcentration.

Another important factor has been found to be the relative angularlocation of the channel 66 to the cutwater defining the narrowest partof the volute 14. In a pump in accordance with the invention, such angleis preferably in the range from 120 to 180, measured in the direction ofrotation, although for clarity in the drawing it is shown as just 150.Experience has shown that the selection of such angle can criticallyaffect the separating action. Optimum results under the operatingconditions generally encountered with aircraft operating up to say25,000 feet altitude have been realized with the angle of 150 as shown.

While we have shown a particular embodiment of my invention, it will beunderstood, of course, that We do not wish to be limited thereto sincemany modifications may be made, and we therefore contemplate by theappended claims to cover any such modifications as fall Within the truespirit and scope of our invention.

We claim:

1. A pump for delivering fluid under pressure and simultaneouslyseparating vapor bubbles occluded in the fluid therefrom comprising acentrifugal impeller, a casing defining a pump chamber including avolute for receiving the discharge of the impeller, said impeller havinga plurality of vanes, said vanes having an interior boundary constitutedas a surface of revolution forming the eye of the impeller for inlet offluid to the vanes, a portion of said casing defining an inlet throatsubstantially coextensive with the radial cross section of said eye andan inlet channel for the liquid and its therein-occluded vapor incommunication wtih said throat, a driving source, a hub forming part ofsaid impeller driven by said source, said vanes being carried at one endon said hub and the free ends whereof, in rotation, sweeping out anannular area positioned in a plane normal to the axis of rotation, ashoulder on said casing contiguous to said free ends positioned in aplane normal to the axis of rotation and juxtaposed to said first plane,said shoulder having an annular groove substantially coextensive withsaid annular area opening in said second plane and confronting said freeends of said vanes, said volute receiving liquid discharged from saidvanes and said groove receiving vapor accumulating at the innermost zoneof said vanes, and a source of suction in communication with said groovefor providing a force through said groove for removing the vapor.deliveredthereto from said vanes.

2. A pump in accordance with claim 1 wherein said source of suction is apump of the Water ring type.

3. A pump for delivering fluid under pressure and simultaneouslyseparating therefrom vapor bubbles occluded in the fluid comprising acentrifugal impeller, a casing defining a pump chamber including avolute for receiving the discharge from the impeller and a substantiallyfrusto-conical inlet throat disposed in an axial direction to one sideof the volute and coaxial with the impeller rotational axis, saidimpeller having a plurality of vanes terminating in part at their outerperiphery on a frusto-conical surface congruent with the wall of saidthroat andseparated therefrom by a space suflicient to provide runningclearance therebetween, said vanes terminating inwardly of the impellerto define a frusto-conical eye inverted with respect to the slope of theouter periphery of the vanes whereby to provide vanes narrower at oneend than at the other and terminated in blunt ends lying in an annularzone normal to the axis of rotation, said impeller having a hubwhereupon the wider ends of the vanes are supported, a portion of saidcasing defining a shoulder extending inwardly substantially at thesmaller diameter of said throat positioned in a plane parallel to saidannular zone, said shoulder having a circular groove therein confrontingsaid annular zone and separated therefrom by running clearance, saidshoulder defining a central opening substantially coextensive with theeye of the impeller and providing an inlet passage to the impeller, asource of suction and means forming a fluid passage from said groove tothe inlet of said source for withdrawing vapor bubbles from theinnermost extent of said vanes toward and into said groove.

4. A pump in accordance with claim 3 wherein said passage-forming meansincludes a conduit in fluid communication with said groove, said voluteincludes a cutwater and the axis of said conduit is displaced angularlycounter to the direction of rotation of said impeller by an angle ofsubstantially 5. A pump for delivering fluid under pressure andsimultaneously separating therefrom vapor bubbles occluded in the fluidcomprising a centrifugal impeller, means defining a casing for the pumpincluding a volute for receiving the fluid discharge from the impeller,said impeller including a hub member and a plurality of vanesoutstanding therefrom, said vanes collectively having a mutualcylindrical periphery for a portion of their axial extent beginning atthe junction with the hub member and said periphery continuing as afrusto-conical boundary to the free end of said vanes whereby said vanesare blunt and narrower radially at their free end than at the hub end,said vanes terminating centrally on a surface which is a surface ofrevolution to define an inlet eye for the impeller, said casing havingan inlet passage substantially coextensive cross-sectionally with thecross-sectional transverse extent of said surface of revolution, meanson said casing defining an annular groove opening toward the blunt endof said vanes, the open face of the groove being substantiallycoextensive with the annular area swept out by the blunt ends of thevanes and separated therefrom by running clearance, said voluteincluding a cutwater, conduit means connecting said groove and the areaof the eye of said impeller, and the junction of said conduit means withsaid groove being displaced angularly from the tip of the .cutwatercounter to the direction of rotation by an angle in the range of from120 to References Cited in the file of this patent UNITED STATES PATENTS2,392,128 Dinsmore Jan. 1, 1946 2,422,956 Edwards June 24, 19472,581,828 Adams Jan. 8, 1952 FOREIGN PATENTS 654,854 Great Britain Feb.27, 1948

